of pittsburgh



March 8, l932. C. J. LIVINGSTONE ,848,636

SEPARATION AND PURIFICATION OF' WAX Filed Sept. 26, 1950 Conf/'110005Chil/ens &mbl`n ed Caffe, Combi ed )T/finie.

Sfr/opina @la/wf; No.1 y

5o/bern* /Va/feap l To MIZ/IVG Tara/f No.1.

Clarence J- Livi ngsone wf@ M@- Ql Patented p Mar. 8, 1932 TED STATESPATENT oFFIcE CLARENCE J'; LIVINGSTONE, 0F PITTSBURGH, PENNSYLVANIA,ASSIGNOB. TO GULF RE- FIN ING COMPANY, OF PITTSBURGH, PENNSYLVANIA, ACORPORATION OF TEXAS SEPARATIN .AND PURIFICTION 0F 'WAX -Application ledSeptember 26, 1930. 'Serial No. 484,658.

This .invention relates to the separation and purification of wax; andit comprises a process. of separating commercially pure wax fromwax-containing mineral oils by 5 mixing the said materials with a liquiddif.

ferential solvent mixture containing both good solvents for wax and poorsolvents for;

wax, lchilling the liquid mixture, precipitating wax therefrom,separating residual 10 liquid mixture therefrom into at least threeparts comprising wax-free residues, the good solventsffor wax and thepoor solvents for wax, suspending theseparated wax in the said poorsolvents, chilling the suspension, separating wax therefrom; theseparated wax being thereafter advantageously washed with additionalpoorsolvents; stripping the poor solvents from the wax thereby recoveringthe so purified wax, uniting the recovered poor solvents with anywashings and with the said separatedvgood solvents vand returning the soreconstituted differential solvent mixture to the first step in theprocess; all as more fully hereinafter set orth and as claimed. f

The removal and recovery of wax from heavy uncracked mineral oildistillates and residua has always presented a diicult problem for theoil industry. While the wax .may beseparated from'the lighter uncrackeddistillates and from slightly heavier cracked` distillates bymerechilling and filtering, any

wax separated in thisl manner from the' heavier fractions and residua,such as cylinder stocks, is precipitated in an amorphous form known aspetrolatum. Separation of this productby the filter press is obviouslyl' impossible.

cold gravity separation or byv a centrif gp.

40 Moreover, these oils are too viscous tof e k processed at ordinarytemperatures in 4these ways and require dilution. A heavy naphtha is'commonly used .as a diluent in the ratio of about 2 volumes of naphthato l of oil.' The naphtha aids in the wax separation in chilling. Waxremoval may befaccomplished on the crude oil after distillation forseparation vof the gasoline, kerosene and gas oil fractions only, andhence 'before the viscosity has be'- come too great for processing. Alltypes of Separation is 'made either by waxes may be precipitated bychilling, vary ing from hard paran, through ceresin-like products andfinally to petrolatum jelly.

In wax-recovering processes using chilling, the lchilling reduces thesolvent power of the wax-bearing oil for wax and causes a separation orprecipitation of wax in discrete particles; amorphous or crystalline, asthe case may be. In diluting the oil with lighter liquid to reduce theviscosity, the solvent power for wax of the added liquid becomesimportant. In algeneral way, the solventpower of light hydrocarbons forwax is less Vthan that of the heavy oils; and the customary dilution ofheavy oil with naphtha therefore gives a better separation of wax inchilling. I have found that, for various reasons, it is better to use asa viscosity reducing diluent, a composite liquid containing a goodsolvent for wax as well as a poor solvent. With certain of thesemixtures, a separation of the precipitate in crystalline form ispromoted.

The so-called heavy wax distillates made by steam distillation aretermed unpressable distillates due to the fact that the wax is.precipitated in an amorphous form which is difficult to filter press,and such distillates are usually subjected to a redistillation undercracking conditions using minimal amounts of steam. The hightemperatures act in some unknown manner to change the wax to acrystallizable form, readily filtered oil.

Various methods have been proposed,

chiefiy dealing with the recovery of paraffin from tarry residues of'coal distillation, for

separating the parain by means of various i diluent liquids of thenature of those called slvents. Mixed solvents have been proposed. Ithas also been suggested to apply these methods to the removal of waxfrom mineral oil distillates-and residua. But these rhmethods have beenin practice adopted only tillation-would have been eliminated by theiradoption. Y

Wax may be separated in filtrable form by the use of certainsolvent'mixtures from oils which, by usual processes, would separateamorphous wax; a form more diicult to handle. This gives a decidedadvantage to these methods. It has been proposed to` use mixtures of twosolvents for this purpose, in one of which the wax is more soluble thanthe other. The latter component then acts asV a precipitating agent,somewhat in the manner that alcohol acts in the ether-alcohol method. vIhave reduced the solvent loss to a negligible point and have effected aconvenient and inexpensive method of purifyin the wax at the same time.

y process can be more conveniently understood by following the varioussteps in connection with the accompanying figure which shows a flowsheet of my process. In this illustratim, the several steps are shownseriatim. A 4 VVax-bearingv oil is mixed with a diiferential solventmixture, containing both good solvents for wax and poorsolvents for wax,in mixing tank No. 1. It is then run through continuous Chillers whereinthe temperature may be reduced to the neighborhood of'minusl 20 F. Thewax is filtered oif, the filtrate being stripped and thereby separatedinto three components `comprising wax-free oil, the

ood solvents for wax and the poor solvents or wax. The lter cake is thensuspended in mixing tank No. 2 with a quantity of the poor solventsVfrom the stripping column. This mixture may be heated, if desired,until the wax dissolves. The mixture is then chilled to a temperature atwhich the wax is practically insoluble in the poor solvent, whichtemperature may be, for example, from 15 to 30 F. and again iiltered infilter No. 3; The filter cake may then be washed with additional poorsolvents. Alternatively, the' wax cake may be' suspended in andrepeatedly` washed by the poor solvent without dis ksolving it. Thefilter cake is then conveniently melter and run through strippin columnNo. 2 to remove the last traces'o solvent. The wax might be separatedinto fractions in the stripping column but this separation can be moreconveniently madein a Subscquent vacuum distillation as indicated on theHow sheet` The distillate from stripping column No. 2 and the filtratefrom lter No. 3 are mixed with the good solvents recovered fromstripping column No. 1 and the whole is then returned to mixing tank No.1V to be mixed with afresh batch of wax-bearing oil. By using continuousiilters and chillers throughout, the whole process may be madecontinuous.

In the process outlined above, the chilling steps' are not necessarilyrequired The whole process can be operated at ordinary temperatures.'Ihe mere mixing of the wax bearing oils'with some types of differentialsolvent mixtures may cause separation of the wax, which separation, ofcourse, usually becomes more complete upon chilling. The chilling of themixture of wax-with poor solvents in mixing tankNo. 2 can also bedispensed with in the same manner.

Another modification which is' sometimes advantageous is that of mixingthe separated good solvents with wax bearing oils in mixing tank N o. lvbefore adding the 'poor solvents recovered from the filtrate anddistillate. This frequently results in a cleaneil precipitation of thewax, the separation being.

sometimes cleaner than that obtained in case a mixed di'erential solventis added directly to the wax bearing oil. The mixtureA of the waxbearing oil with the good solvents may be chilled before, after orduring the addition of the poor wax solvents. L

Rather a wide selectionof good and poor solvents may be used in myprocess. Among Vthe good solvents may be lnentioned benzol, naphtha,carbontetrachlorid, toluene, xylene and other products having about thesame solvent power for wax. The poor` solvents may comprise acetone,ethylene dichlorid, propyl'ene diohlorid, ethyl alcohol, isopropylalcohol, the butyl. alcohols and the like. Mixtures of these poorsolvents may be used. Itis advantageous to use good solvents and poorsolvents having appreciably different boiling'point'ranges, in orderthat these may be readily separated as two fractions in the strippingcolumn. A clean separation is, of course, not essential. A partlcularlyadvantageous composition which I have usedroxrprises benzol andethylenedichlorid in the ratio of about 3 parts to 7 by weight.

My process may be used to separate wax from a great variety of mineraloil residues and distillates. I have tested the method with various waxdistillates and have found that the wax distillates generally'producedcanv be reduced by at least 1/,2 and still give satisfactory results.Coke still slops; acid treated, clay contacted cylinder stocks;unpressable distillates; reduced crudes; and bright stocks from unressable distillates, etc., from various oil fieids have given excellentresults.

Wax can also be extracted from tarry residues, such as thoseproduced inthe low temperature carbonization of coal, by my process. Only minorchanges in manipulation are required. Wax separated by other processescan be purified by my method, which would .then consist in dissolvingthe wax in the differential solvent mixture and proceeding further asdescribed previously.

In a specific embodiment of my invention, representing an actualoperation, I took 1000 parts of Wax distillate and reduced this to 750parts by distillation lbefore mixing with my differential solvents.These were mixed in the proportions by weight of 80 parts of the reducedwax distillate, 36 parts benzolY and 84 parts ethylene dichlorid. Thismixture was chilled, cooling the same to about minus 26 F. The wax wasfiltered off and the filtrate stripped to separate it into itscomponents, the oil recovered having a cold test of from minus 20 F. tominus 30 F. The recovered body of ethylene dichlorid was divided, 60parts being used to suspend the wax filter cake. This suspension washeated to the neighborhood of 70 F., (approximately suflicient to'dissdlve the wax) and then chilledI to plus 15 F. The wax was againfiltered off and washed with the remaining .ethylene dichlorid. Thewashed filter cake was then put through a stripping column, removing thelast traces of solvent. The recovered distillate, containing principallyethylene dichlorid, was united with "the filtrate from the previousoperation andl then the separated benzol Was added, the whole formingV areconstituted differential solvent mixturerto be used in the first stepof the process. The solvent loss was practically negligible.

The wax recovered was a semi-refined wax, white and dry and with anunexpectedly low oil content. The low pour test of the oil was alsohighly satisfactory from an operating standpoint.

In the above example 5 to 10 per cent of the benzol can be replaced withpetroleum nanhtha, without appreciable change in operating conditions.-The proportions of ethylene dichloridand benzol'can be varied, providedcorresponding changes are made inthe 'temperatures employed. Mixtures ofthe solvents be completely separated from the poor solvents. It is onlyrequired that two cuts be produced, one of said cuts being a poorsolvent for the wax.

By using the poor solvents for purifying and washing the wax cake, aconsiderably higher yield and a whiter product is obtained. The poorsolvent for the wax serves to dissolve oil from the cake as well as anygood solvents remaining therein and, upon chilling, the wax isprecipitated from a liquid in which it is but very slightly soluble-Hence but little of the solvent is dissolved in the Wax and vice versa.The separation is practically complete. Any solvent entrained by the Waxis also more readily removed in the stripping operation. It isundoubtedly due to these factors that m process gives a higher yield ofboth oil andywax, a more highly refined wax and a wax-free oil oflowerpour test than processes heretofore proposed.

vBy my method I am enabled to use a wax distillate which has beenreduced to the point where the solar fraction is removed. In fact it iseven possible to satisfactorily dewax a distillate containing someportions of 'ordinarily unpressable wax while still recovering a goodwax. This results in a considerable reduction in the cost of theoperation as a whole. The pour points obtained for the waxfree oil areconsiderably lower than those obtained by prior methods. The yields ofboth oil and wax are high and a white; dry, hard wax is obtained,suiiiciently pure to serve as a semi-refined product without the use ofsweating.

vIt is obvious that many modifications may be made in my process withoutdeparting from the spirit of my invention.

What I claim is 1. In the separationv and purification of solventmixture containing poor wax solvents and good wax solvents, chilling themixture, separating the Wax from the mixture separating the solventsfrom residual liquid andk thereafter further purifying the separated Waxby treatment-with the said poor solvents.

3. In the separation and purification of wax from wax containing mineraloils and tarry residues, the process which comprises mixing thel saidmaterials with a dierential solvent mixture containing poor wax solventsloo l and good Wax solvents, separating the wax from the residualsolvent mixture, stripping the said residual solvent mixture to therebyseparate and recover wax free residues, the poor Waxsolventsand the goodwax solvents,

- suspending the separated Wax in the recovsolvent mixture containingpoor Wax solvents ered poor solvents. and separating and recovering waxfrom the said suspension.

-4. In the separation and purification of Wax from Wax containingmineral oils and tarry residues, the process which comprises mixing thesaid materials with a differential and good'wax solvents, chilling themixture, separating thewax from the residual solvent mixture, strippingthe said residual solvent mixture to thereby separate and recover waxfree residues, the poor wax solvents and the good Waxsolvents,suspending the separated AWax in the recovered poor solvents, chillingthe suspension and separating and recovering v wax from the saidsuspension'.

7 5. In the separation and purification of wax'from'wax containingmineral oils and tarry residues, the process which comprises mixing thesaid materials with a differential solvent mixture containing poor Waxsolvents and good wax solvents, separating the Wax v from the residualsolvent mixture, stripping same and to recover poor wax solventstherefrom.

, 6. In the separation andpurificationofwax from wax containing mineraloils and tarry residues, the process which comprises mixing the saidmaterials with a differential solvent mixture containing poor Waxsolvents and good Wax solvents, chilling the mixture, sep- Carating ltheWax^from the residual solvent mixture, stripping the said residualsolvent mixture to thereby'separate and recover wax' free residues, thepoor Wax solvents andthe good Wax solvents, suspending the separated waxin the recovered poor Wax solvents, chills ing\the suspension,separating the wax from l the said suspension, washing the separated.Wax with additional poor Wax solvents and stripping the Washed Wax Ytopurify the same and to recover poor Wax lsolvents therefrom.

7. In the separation and purification of wax from Wax containing mineraloils and tarry residues, the .process which comprises mixing the saidmaterials with a differential solvent mixture containing poor waxsolvents and good vvax solvents, separating the Wax `from the residualsolvent mixture, 'strip- .ping the said residual solventmixture tothereby separate and recover wax free residues, the poor wax solventsand the good Wax solvents, suspending the separated wax, in therecovered poor Wax solvents, separating and recovering the suspended waxfrom the residual poor wax solvents, and returning the separated andrecovered solvents to serve in a repetition of the process.

8. In the separation and purification oi wax from wax containing mineraloils and tarry residues, the process which comprises mixing the saidmaterials with a diferential solvent mixture containing poor Waxsolvents and good wax solvents, chilling the mixture, separating the waxfrom the residual solvent mixture, stripping the said residual solventmixture to thereby separate and recover Wax free residues, the poor Waxsolvents and the good Wax solvents, suspending the separated wax in therecovered poor Wax solvents, chilling the suspension, separating andrecovering the suspended Wax `from the residual poor Wax solvents, andreturning the separated and recovered solvents to serve in a repetitionof the process.

9. In the separation and purication of Wax from Wax containing mineraloils and tarry residues, the process which comprises mixing the saidmaterials with a differential solvent mixture containing poor Waxsolvents and good Wax solvents, separating the Wax from the residualsolvent mixture, stripping the said residual solvent mixture to therebyseparate and recover ,Wax free residues, the poor Wax solvents and thegood Wax solvents, suspending the separated wax in the recovered poorWax solvents, separating the suspendedwax from the said suspension,stripping the poor Wax solvents from the Wax,

recovering the so purified Wax, uniting the poor Wax solvents recoveredin the Wax separating and stripping operations with the recovered goodWax solvents to reconstitute a dierential solvent mixture, and returningthe said mixture t6 the iii'st step in the. process.

10. In the separation and purification of Wax from Wax containingmineral oilsvand tarry residues, the process which comprises mixing thesaid materials with a differential solvent mixture containing poor Waxsol-' vents and good` Wax solvents, chilling the mixture, separating theWax from the residual mixture, stripping the said residual solventmixture to thereby separate and recover Wax free residues, the poor waxsolvents and the 'good Wax solvents, suspending the separated Wax in therecovered poorwax solvents, chilling the suspension, separating the waxfrom the said suspension, stripping the poor Wax solvents from the Wax,recovering the so purified Wax, uniting the poor Wax solvents recoveredin the Wax, separating and stripping operations with the recovered goodWax solvents to reconstitute a dillerential solvent mixture, andreturning the said mixture to the iirst step in the process.

11. In the separation and puriication of Wax from Wax containing mineraloils and tarry residues, the process which comprises mixlng the saidmaterials with a good Wax solvent, gradually adding a poor Wax solvent,separating and .recovering the Wax, stripping the residual solventmixture to thereby separate and recover wax free residues, the poor Waxsolvents and the good wax solvents, and returning the separated andrecovered solvents to serve in a repetition of the process.

12. In the separation and purification of wax from Wax containingmineral oils and tarry residues, the process which comprises mixing thesaid materials with a good wax solvent, gradually adding a poor Waxsolvent, separating and recovering the wax; the mixture being chilledbefore separation ofthe said wax; stripping the residual solvent mixtureto thereby separate andrecover wax free residues, the poor Wax solventsand the good wax solvents, and returning the recovered solvents to servein a repetition of the process.

13. In the separation and purification of wax from Wax containingmineral oils and tarry residues, the process which comprises mixing thesaid materials with a good wax solvent, gradually adding a poor Waxsolvent, separating and recovering the wax, stripping the residualsolvent mixture to thereby separate and recover wax free residues, thepoor wax'solvents and the good wax solvents, suspending the separatedwax in the recovered poor Wax solvents, separating and recovering waxfrom the residual poor solvents, and returning the said residual poorwax solvents and the recovered good Wax solvents to Yserve in arepetition of the process.

14. In the separation andpuriication of wax from Wax containing mineraloils and tarry residues, the process which comprises mixing the saidmaterials with a'good wax solvent, gradually adding a poor wax solvent,separating and recovering the Wax, stripping the residual solventmixture to thereby sep arate and recover Wax free'residues, the poor waxsolvents and the good wax solvents, suspending the separated Wax in therecovered poor Wax solvents, separating and recovering wax from theresidual poor solvents, stripping the poor Wax solvents from theseparated wax, recovering the so purified Wax, and returning therecovered poor wax solvents and good wax solvents to serve in arepetition of the process.

15. The process of claim 1 in which is employed a dierential solventmixture containing ethylene dichloride las a poor Wax solvent and benzolas a good Wax solvent.

16. The process of claim 2 in which is employeda diierential solventmixture containing ethylene dichloride as a poor wax solvent and benzolas a good wax solvent.

17. The process of claim 4 in which is employed a differential solventmixture containlng ethylene dichloride as a poor wax solvent and benzolas a good wax solvent.

18. The process of claim 6 in which is employed a differential solventmixture containing ethylene dichloride as a poor Wax solvent and benzolas a good wax solvent.

19. The process of claim 8 in which is employed a dierential solventmixture containing ethylene dichloride as a poor wax solven and benzolas a good wax solvent.

20. The process of claim 10 in which is employed a differentialsolventmixture containing ethylene dichloride as a poor wax solvent andbenzol as a good wax solvent.

In testimony whereof, I have hereunto affixed my signature.

CLARENCE J. LIVINGSTONE.

